Mud Bay Logging Co 2-6-6-2 "Mallet Mogul" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 8 (Locobase 4057)

Data from Jon Davis's [] . See also DeGolyer, Volume 80, p. 310. Works number was 60412 in March 1928.

For her first twelve years, this engine operated out of Mud Bay, Wash on 30-35 degree curves ( 193-166 foot/ 58.8-50.6 metre radii) and up 7% grades. 8" (203 mm) piston valves served the HP cylinders while 12" (305 mm) did for the LPs. A "Hereafter" note in the specs suggests raising the question about "moving front engine truck forward (making 42" from center line of truck to center line of cylinders). This will provide clearance for removal of exhaust pipes from low pressure cylinders." Another Hereafter note dated 15 December 1934 suggested fitting short springs between the drivers instead of equalizing them as well as "applying a coil spring in the spring hanger ahead of the front driver.

The specifications said that the locomotive should be able to handle 22 loaded cars (1,012 short tons/918 tonnes) down grades of 3.7%. Each car weighed 13.5 tons (12.25 tonnes) empty and 46 tons (41.7 tonnes) loaded and used automatic brakes whose cylinders measure 8" x 12" (203 x 306 mm).

Mud Bay 8 then went to Weyerhaeuser Timber (possibly as part of a merger), was renumbered #6, and worked for another 20 years out of Klamath Falls, Ore.

After being on display for a few years, she was restored to service in 1969 and ran until US Plywood's engine arrived in 1974. She's been partially dismantled and in storage ever since although some thought's been given to reinstating her to service.

Principal Dimensions by Steve Llanso of Middle Run Media

Locobase ID4057
RailroadMud Bay Logging Co
Number in Class1
Road Numbers8
Number Built1
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)16 / 4.88
Engine Wheelbase (ft / m)37.25 / 11.35
Ratio of driving wheelbase to overall engine wheelbase 0.43
Overall Wheelbase (engine & tender) (ft / m)64.02 / 19.51
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)180,000 / 81,647
Engine Weight (lbs / kg)210,000 / 95,255
Tender Loaded Weight (lbs / kg)101,000 / 45,813
Total Engine and Tender Weight (lbs / kg)311,000 / 141,068
Tender Water Capacity (gals / ML)5000 / 18.94
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)1500 / 5678
Minimum weight of rail (calculated) (lb/yd / kg/m)50 / 25
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)44 / 1118
Boiler Pressure (psi / kPa)200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)18" x 24" / 457x610
Low Pressure Cylinders (dia x stroke) (in / mm)28" x 24" / 711x610
Tractive Effort (lbs / kg)42,517 / 19285.41
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.23
Heating Ability
Tubes (number - dia) (in / mm)135 - 2" / 51
Flues (number - dia) (in / mm)24 - 5.375" / 137
Flue/Tube length (ft / m)17 / 5.18
Firebox Area (sq ft / m2)157 / 14.59
Grate Area (sq ft / m2)31.50 / 2.93
Evaporative Heating Surface (sq ft / m2)1927 / 179.09
Superheating Surface (sq ft / m2)466 / 43.31
Combined Heating Surface (sq ft / m2)2393 / 222.40
Evaporative Heating Surface/Cylinder Volume272.72
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation6300
Same as above plus superheater percentage7497
Same as above but substitute firebox area for grate area37,366
Power L15922
Power MT435.19

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Wes Barris